Not Applicable
1. Field of the Invention
This invention relates to the purification of air, particularly in the passenger cabins of motor vehicles, but also in hospitals, nursing homes, other health care environments, and industrial environments, and especially to the use of a plurality of packed bed filter media packets and a HEPA filter placed in a predetermined sequence within a portable air purifier that can be placed as a console/arm rest at selected locations within a motor vehicle cabin, or by some adaptation in a vehicle trunk or bed of a pickup truck, or placed in any of such other environments, and in the case of a vehicle the air purifier operates independently of the vehicle ventilation system.
2. Description of the Prior Art
The literature in the field of Indoor Air Quality (IAQ) may use the term xe2x80x9cambient airxe2x80x9d to refer to the air within an indoor room, while in the context of air quality generally the term often refers to xe2x80x9coutside air.xe2x80x9d For clarity, the term xe2x80x9cambient airxe2x80x9d is used herein in the latter sense, and the air within the motor vehicle cabin that is to be purified is referred to as xe2x80x9ccabin air,xe2x80x9d although that cabin air will of course be continually supplied with xe2x80x9coutsidexe2x80x9d or xe2x80x9cambientxe2x80x9d air by virtue of the vehicle ventilation system, open windows, or the like. More specifically, xe2x80x9cambient airxe2x80x9d herein means that air through which the vehicle is being driven.
Considerable effort has been directed toward reducing air pollution inside the cabin of motor vehicles. With hundreds of different kinds of air pollutants around and inside motor vehicles traveling on congested highways, this is no easy task. Most of this effort has targeted dust, pollen, and some odors. Vehicle manufacturers in Europe, Japan and the USA now offer air filtration subsystems for the passenger cabins of some of their new automobiles. These subsystems are typically placed within the ventilation system of new cars and serve as gross particulate filters. Some of these subsystems also have small amounts of activated carbon to reduce odors. These ventilation subsystems are intended to capture particles that are 3 to 8 microns in diameter and larger, but they are not designed to reduce substantially the extensive fine (2.5 micron in diameter and smaller) particulate matter over any extended period of time.
Some of the particulate filters now being installed in the ventilation systems of new cars use electrostatic non-woven filter media. The electric charges on these media help to capture fine particulate matter; however, as the filter media fills, the charge and thus the effectiveness of such media are diminished. The majority of particles by number that appear in the cabin air environment in fact fall within the size range of less than one micron in diameter. These submicron particles are not effectively reduced by current ventilation subsystem designs, but yet they present the greatest health hazard to human beings since they penetrate deeply into the respiratory tract. Also, placement of filters that contain activated carbon within ventilation system does capture some gases, but with no specific standard of effectiveness for individual gases, the object seemingly being simply that of reducing xe2x80x9codorsxe2x80x9d for purposes of customer satisfaction, but with little or no thought being given to the reduction of any identified pollutants. One major limitation inherent in such systems also is that they have been designed to minimize pressure drop in order to maintain a strong flow of air, for purposes of heating or cooling, but as a result any actual fine particle purification of the air being circulated becomes minimal.
Some inventors have proposed stand-alone cabin air filter systems that are to be permanently mounted in the trunk, the rear window deck, or the ceiling (head liner) of automobiles. Again, most of these proposed systems are designed as gross particulate filters, with small amounts of activated carbon added to reduce smoke and generic odors. These, too, have had little or no capacity to rapidly filter and re-circulate cabin air. Some of these devices are small electronic air cleaners that target fine particulate matter, but also have the potential for generating ozone, itself a pollutant. Such devices also require frequent cleaning to prevent arcing and to minimize ozone production.
In most cases, the stand-alone devices of the prior art have had insufficient air flow to reduce substantially the continuing flow of pollutants that comes into the vehicle cabin through the ventilation system, and through leakage around doors and windows. No device heretofore proposed is portable, re-circulates cabin air at effective rates of cubic meters per minute (m3/min) or the corresponding cubic feet per minute (CFM), and employs a specific sequence of filters that has been especially designed to remove specific pollutants, including fine particulate matter, lead, carbon monoxide, ozone, sulfur dioxide, nitrogen dioxide, benzene and other hydrocarbons. A number of the filters used in the invention are of the packed bed type, which type has a long history with respect to purifying air in buildings, but to the inventor""s knowledge, there have been no successful attempts to adapt the packed bed technology to cabin air purification. Also, no prior art device intended for vehicle cabin air purification that is known to this inventor has targeted the specific air pollutants for which the EPA or other agencies have established ambient air quality standards, with the goal of reducing the concentration levels of those pollutants at least to below the defined health standards. This seems to have resulted (a) from not being aware until the last several years of the high levels of pollutants that are actually found in a vehicle cabin while driving through crowded urban streets; and (b) from emphasizing in research what particular vehicle manufacturers were doing about cabin air pollution rather than on what needed to be done if those high levels of pollution were to be reduced. Perhaps most significantly, the inventor is aware of no prior test data, such as those reported herein, in which an air purifier was installed in a vehicle that was then driven through the streets, while collecting air quality measurements both with the purifier operating and with it not operating, so that by comparison of those data a practical measurement of the efficacy of the purifier could be established.
Particular patents known to the inventor that relate to air purification, especially in the cabins of motor vehicles, will now be described. U.S. Pat. No. 3,722,182 issued Mar. 27, 1973 to Gilbertson touches on the use of an air filtering device mounted on the rear window deck of an automobile and functions independently of the heater/air conditioner/air intake (plenum) system of the vehicle. (An alternative embodiment that connects directly to the air intake of the vehicle is also described.) For removal of particulate matter, the device employs electrostatic plates, although in the more recent state of the art it is known that HEPA filters better serve that purpose, and do not require the frequent cleaning or replacement that is necessary for electrostatic systems.
U.S. Pat. No. 3,883,637 issued May 13, 1975 to Benedict describes an activated charcoal filter element having dispersed mixtures of copper and chromium oxides, chromates, dichromates and the like for purposes or removal of H2S and catalytically, similar air-borne sulfur compounds such as mercaptans, organic sulfides, thiophene compounds, thioethers and organic sulfoxides.
U.S. Pat. No. 3,870,495 issued Mar. 11, 1975 to Dixson, et al., describes the use of non woven fibers of wood, paper, hemp and the like to avoid having periodic gaps in the material as is characteristic of woven fabrics. Secondly, the filters are used in multi-layer or laminated form so as to block any gaps that might occur by way of manufacturing imperfections with respect to particular pieces of fabric.
U.S. Pat. No. 4,207,291 issued Jun. 10, 1980 to Byrd et al. describes the use of a fabric substrate impregnated with MnO2 for the removal of ozone from the air in aircraft cabins.
U.S. Pat. No. 4,610,703 issued Sep. 9, 1986 to Kowalzyk describes a single filter installed within a vehicle heater/cooling system.
U.S. Pat. No. 4,629,482 issued Dec. 16, 1986 to Davis describes a portable air purifier for use in rooms (as opposed to vehicle cabins) that employs a HEPA filter for particulate removal and operates on AC power. The need to replace the filters after long use is shown to the user externally by the appearance of a pulsation in the air flow rate. At an initial stage with a clean filter, operation occurred at a measured air flow rate of 350 cubic feet per minute (CFM).
U.S. Pat. No. 4,658,707 issued Apr. 21, 1987 to Hawkins et al. describes an air purifier for vehicle interiors, disposed principally within the headliner, that includes a fan and smoke filters, together with a smoke detector that automatically initiates operation of the device upon the detection of smoke.
U.S. Pat. No. 4,722,747 issued Feb. 2, 1988 to Armbruster describes an air filter system to be mounted by bolts beneath the roof of a vehicle and including a pair of blowers dispersed at opposite ends of the device for blowing out air, an air intake opening in the middle, and both foam and activated charcoal filters interposed there between.
U.S. Pat. No. 4,917,862 issued Apr. 17, 1990 to Kraw et al. describes a filter system for the removal of mercury, bacteria, pathogens and other vapors, especially with respect to mercury vapors in a dental office. A sequence of filters includes a fibrous pre-filter, then a filter having a honeycomb structure or the like, within which a plurality of cells are partially filled with activated carbon pellets, and then preferably a post-filter. The quantity of pellets introduced may lie between 30% and 90% of the total cell volume, whereby the pellets are xe2x80x9cswirledxe2x80x9d in the air stream passing through the filter, this motion of the adsorbent pellets being intended to increase adsorbent-adsorbate contact. Operation of the device at air flow rates of at least 700 CFM is said to be preferred, although operation at rates up to 1200 CFM is also noted.
U.S. Pat. No. 5,004,487 issued Apr. 2, 1991 to Kowalzyk describes an air filter assembly for use in passenger compartments of motor vehicles that is installed within the vehicle heating/cooling system and is air pressure driven to clean the air coming into the vehicle. A sensor provides warning when the filter needs cleaning or replacement.
U.S. Pat. No. 5,192,346 issued Mar. 9, 1993 to the same inventor (Kowalzyk) employs a pleated flat filter to permit greater air flow.
U.S. Pat. No. 5,042,997 issued Aug. 27, 1991 to Rhodes describes an environmental control system for a building which includes an air filter that has a series of particulate filters and a chemical and activated charcoal filter.
U.S. Pat. No. 5,221,292 issued Jun. 22, 1993 to Aoyams describes an air cleaning system for vehicle passenger compartments which includes two air cleaners: a single air cleaner for cleaning passenger compartment air when the pollution level is low; and a second cleaner for conditions of high pollution within the vehicle is drawing in and cleaning outside air, while the first cleaner discharges compartment air to the outside.
U.S. Pat. No. 5,683,478 issued Nov. 4, 1997 to Anonychuk describes an air filter device featuring a bottom base unit having a hollow cylindrical filter unit to be housed within an existing blower motor assembly under the hood of a car.
U.S. Pat. No. 5,879,423 issued Mar. 9, 1999 to Luka et al. describes a filter system having a filter body in the form of a plate-like filter element exemplified by an xe2x80x9cactive carbon matxe2x80x9d disposed between at least two planar frame parts, wherein two such frame parts enclose the filter element and are then held together by snaps, the structure further permitting construction of an array of such filter elements in series, and the system as a whole being intended to be part of the air conditioning system of the vehicle.
Some effort has been made to provide air purification, or at least some attention to vehicle cabin air quality, in add-on or after-market devices. For example, the web site http://www.realgoods.com/shop/shop.1.cfm?dp=107andts=1053857 operated by Real Goods offers a three-stage auto air filter that employs activated carbon, an electret charged medium, and a Zeolite VOC (xe2x80x9cVolatile Organic Compoundsxe2x80x9d) filter, but the efficacy of the device is not known, other than claiming to recycle the cabin air in about six minutes. The site http://www.realgoods.com/shop/shop.1.cfm?dp=107andts=1053856 from the same company offers an auto ionizer to help precipitate air pollutants, but nothing is said about either air circulation or tested effectiveness. (Both sites visited Dec. 17, 2000.)
Some technical literature has also addressed cabin air purification, for example, in the article by Heinz H. Bitterman entitled xe2x80x9cHistory and World Wide Trends in Cabin Air Filter Testing,xe2x80x9d published in Fluid/Particle Separation Journal, Vol. 3, No. 2, August 2000, pp. 152-155. This article points out the air test standards currently being employed in Europe, which are then compared to the less stringent U.S. standards. (The article notes, for example, that General Motors vehicles for the European market will have filtration for both particles and odors, whereas the American versions of such vehicles will only have particle filters.) The article also remarks that xe2x80x9cif it could be managed to provide filters being effective with diesel soot, a major step to recognizable air quality improvement inside cars would be made,xe2x80x9d but only the use of activated carbon as a filter material, and not the HEPA filter, which the present data indicates is necessary (to remove the fine particulates onto which many of the other pollutants appear to adhere), is proposed to reach that goal. Bitterman also provides no experimental data collected from moving vehicles, as are the data provided herein.
An article by Tadeusz Jaroszczyk et al. entitled xe2x80x9cFiltration Performance of High Efficiency Cabin Filters for Operators"" Protection in Dusty Environments,xe2x80x9d published in Fluid/Particle Separation Journal, Vol. 3, No. 2, August 2000, pp. 156-164 (Jaroszczyk I), discusses the cabin air filtration systems of mobile mining equipment with respect to the efficacy of particular filter types, and also both recirculating and air intake ventilation systems. The article discusses minimum air flow rates (e.g., 43 m3/hr=25.3 CFM), a xe2x80x9cnominalxe2x80x9d air flow rate of 100 m3/h being used in the reported laboratory tests, filter pressure drops (e.g., 20 Pa), and xe2x80x9cdust capacity,xe2x80x9d a parameter for use in high dust environments.
An article by Tadeusz Jaroszczyk et al. entitled xe2x80x9cMedia Needs for Automotive Cabin Air Treatmentxe2x80x9d published in Proceedings, Filtration ""94 Conference, American Filtration and Separations Society, pp. 123-147 (Jaroszczyk II), sets out criteria that filter media should meet in order to be used in cabin air filtration. Particular stress is given to the constraints that are present in ventilation system filter design, in light of the (presumed) limited space available for such filtration, as well as a perceived need to maintain a high air velocity for purposes of heating, ventilation and air conditioning (HVAC), with the resultant short residence time of the air within the filter system being said to reduce filter effectiveness. The article indicates, e.g., (p. 125), that xe2x80x9cconventional high efficiency filters operate at low filtration velocities and excessively large spaces would be required to accommodate these filters in a car,xe2x80x9d and(p. 126) that xe2x80x9ccurrent ventilation system designs do not allow for the incorporation of conventional high efficiency filters (HEPA) typically required if xe2x80x98lung damagingxe2x80x99 particles have to be removed.xe2x80x9d
The proposed solution, but for which no specific means are given, is noted (p. 130) as follows: xe2x80x9cAn independent car ventilation system with recirculating air flow should be used to control contaminants from internal sources. Filters in this system can be installed in the trunk, under the roof (in the headliner), or under the seats. Since there is more space in these locations, such filters can be larger than ventilation system filters. A low flow velocity in these filters can be maintained so that high filter and adsorber efficiency can be achieved.xe2x80x9d The article also discusses odor reduction and the air velocity values used in laboratory tests, indicating (pp. 145-146) that with respect to odor control, xe2x80x9cunder the flow conditions common in this application, adsorbent media did not have sufficient efficiency and life to remove challenge substances.xe2x80x9d
An article by Ogaki et al., xe2x80x9cThe Road Test of Car Cabin Filters in Japan,xe2x80x9d Fluid/Particle Separation Journal (American Filtration and Separation Society), Vol. 11, No. 1, April, 1998 (pp. 101-106) describes the testing of a number of filter types, including a two-layer dust removal type having a prefilter mainly composed of polyester fiber and a binder, and a micro fiber layer composed of melt-blown polypropylene. A four-layer type combines that dust removal type with another two layers intended to remove odors, comprising a layer of activated carbon granules disposed on a polyester backing layer. The article also sets out the Japanese Environmental Standard for suspended particulate matter (SPM) (which was said to be satisfied nowhere in Tokyo) and reports roadside measurements made by the Japanese Environment Agency for sulfur dioxide, nitrogen dioxide and hydrocarbons, as well as efficiency data for the various filters derived in this study, but no attempt is made to relate this efficiency study to the achievement of any environmental standard. Road tests of odor perception and dust concentration were also taken, and showed a clear correlation between odor perception and peaks in measured dust concentrations, the observance of these being attributed to vehicle exhaust gas.
An article by Samuel E. Lee, et al. of the Ford Motor Company entitled xe2x80x9cOdor Filter Design Process,xe2x80x9d Fluid/Particle Separation Journal (American Filtration and Separation Society), V. 9 No. 3, October 1996, pp. 185-190, addresses cabin air filtration in terms of (1) the constraints (high air flow, low pressure drop, small package size) placed on any system that will be incorporated into a vehicle HVAC system and (2) customer perception of odors, without reference to any directed attempt to attain positive health benefits or the meeting of air quality standards. The article also states that xe2x80x9cin most cases, the odor filter is intended as a customer comfort feature rather than a health and safety feature,xe2x80x9d and further that the filter design process is to depend significantly on xe2x80x9cwhat the customer wants,xe2x80x9d which in turn is to be based on market research. Some laboratory comparisons of filter performance, at face velocities of approximately 0.75 m/sec and 340 m3/hr flow rates, are also reported.
This industry emphasis on low pressure drops and customer comfort is probably best shown in a practice noted in the article by Olaf Kievit, xe2x80x9cCabin Air Filter Loading Under Real-Life Conditions,xe2x80x9d Advances in Filtration and Separation Technology (American Filtration and Separation Society), V.11, 1997, pp. 188-192, wherein the end of a filter""s xe2x80x9cuseful lifexe2x80x9d is defined as that point at which the pressure drop exceeds 1000 Pa, which as to one test occurred after only 30 hours. The issue addressed by the present invention is not that of any such pressure drop, but rather the question of whether the filter is still able to reduce cabin air pollution levels to below government standards, under ambient air conditions in which those levels far exceed such standards when the invention is not in use. (It is shown by the present invention that the industry concern for low pressure drops may be misplacedxe2x80x94an air purifier external to the HVAC system of a vehicle can not only be provided, but can be provided so as to add further utilitarian and indeed aesthetic value to the vehicle. Placement of the air purifier external to the vehicle HVAC system eliminates that pressure drop as a major issue of concern.)
The web site http://www.epa.gov/ttn/amtic/pmspec.html, under the heading xe2x80x9cA final draft copy of the xe2x80x9cParticulate Matter (PM2.5) Speciation Guidance Document,xe2x80x9d at pp. 24-31 (pp. 15-22 as printed), describes in detail the general characteristics of PM2.5 particles, identifies the xe2x80x9ctarget speciesxe2x80x9d for which speciation of the chemical components in test analyses of air is sought by the U.S. Environmental Protection Agency, and in particular identifies a very wide range of pollutants in this PM2.5 category, and their sources, that become a part of our every day air. (Site visited Dec. 17, 2000.)
To emphasize further the social importance of this issue, more recent research has shown that the concentration level of major air pollutants in the passenger cabins of vehicles operating on congested highways is typically 1.5 to 10 times higher than the level found at nearby monitoring stations. The data in the following Table I (wherein MTBE is methyl-tertiary butyl ether, MQL means xe2x80x9cbelow quantification limit,xe2x80x9d i.e. not detectable, and xe2x80x9cLAS-Xxe2x80x9d is a type of optical particle counter) were reported by the California Environmental Protection Agency Air Resources Board as Release 99-18 on Jun. 10, 1999, as an Executive Summary entitled xe2x80x9cMeasuring Concentrations of Selected Air Pollutants Inside California Vehicles,xe2x80x9d of a research study that included data collection in both Los Angeles and Sacramento (only the Los Angeles data are shown here).
Because the levels found at road-side monitoring stations in many major cities now exceed in themselves the health standards established by the U.S. EPA, the much higher levels of those same pollutants inside vehicles can present an even more significant health risk to passengers.
This same problem exists worldwide, and is rapidly getting worse. As just one example of that, the article xe2x80x9cUrban Air Quality Management Strategy in Asiaxe2x80x94Jakarta Report (World Bank Technical Paper No. 379, 1997), Jitetendra J. Shah and Tanvi Nagpal, Eds. pp. 1-2, has expressed the following in an Executive Summary to the report:
Larger and more diverse cities are a sign of Asia""s increasingly dynamic economies. Yet this growth has come at a cost. Swelling urban populations and increased concentration of industry and automobile traffic in and around cities has resulted in severe air pollution . . . .
Jakarta""s population doubled between 1981 and 1991 . . . . In 1995, the metropolitan area""s population was 11.5 million. This growth was accompanied by a tremendous rise in the number of vehicles on Jakarta""s roads from approximately 900,000 to 1,700,000 . . . .
These developments are reflected in the city""s deteriorated air quality. Pollutant concentrations near the main roads and in the northern part of the urban area are sometimes extremely high. The highest values have been measured in the northern part of Jakarta, but many stations seem to be influenced by local sources. The bus terminals in Pulo Gadung and Cililitan both show average total suspended particles (TSP) values above 300 xcexcg/m3. Overall, traffic and industries are the main sources of air pollution in Jakarta. Total TSP emissions in Jakarta are estimated at 96,733 tons/year. Particulate matter of 10 microns or less (PM10) emissions total 41,369 tons/year, and nitrogen oxide (NOx) emissions are estimated at 43,031 tons/year. TSP concentrations are lower in the outskirts, averaging 100-150 xcexcg/m3. The annual TSP averages in the most polluted areas are 5-6 times the national air quality guideline. Resuspension from roads, diesel and gasoline vehicle emissions, and domestic wood and refuse burning are the main sources of particulate pollution. Drivers, roadside residents, and those who live near large sources are most severely affected.
High ozone concentrations, measured 30 to 40 kilometers outside Jakarta, indicate that secondary pollutants have developed as a result of NOx and VOC emissions in Jakarta . . . .
While attaching an economic value to morbidity and mortality stemming from air pollution can be difficult, there is anecdotal as well as estimated evidence to suggest that the health of Jakarta""s residents is under assault. Dose response equations used for valuing health impacts reveal that PM10 caused a total of 4,364 excess deaths, 32 million restricted activity days (RAD), 101 million respiratory symptom days (RSD), innumerable emergency room visits, asthma attacks, cases of bronchitis in children, and hospital admissions, at a total cost of about US $300,000 (based on Indonesian data) in 1990.xe2x80x9d
Those health risks will of course include the possible spread and inhalation of airborne infectious agents, particularly in the case of vehicles that accept transient passengers as part of their daily function, such as police cars, limousines, taxicabs and ambulances. The following Table II contains a listing of some well known such infectious agent, indicating both the scientific name of the agent and the particular infection(s) that each may cause, and were selected from Joan Luckmann and Karen Creason Sorensen, Medical-Surgical Nursing: A Psychophysiological Approach (W. B. Saunders Company, Philadelphia, 1987), 3d Ed., pp. 120-121.
Such airborne pathogens are to be found in nursing homes and hospitals or the like as well, and as will be noted below, a portable embodiment of the invention equally finds application in that context.
With the exception of certain special purpose applications, such as the Kraw et al. patent that is principally concerned with mercury in dental offices, or the Benedict patent which treats only sulfur compounds (only one of which, sulfur dioxide, ranks as a major criteria air pollutant), and in spite of the EPA documentation of this pressing need for xe2x80x9cspeciationxe2x80x9d of the offending materials, the prior art discloses little attempt to address the issue of motor vehicle cabin air pollution in terms of specific chemical elements or compounds, notably those that are know to be toxic, and/or for which standards for air purity have been defined.
The foregoing literature may be summarized by saying that efforts in the air purification industry, except perhaps in the mining environment and in industrial and office environments under the requirements of OSHA, have primarily emphasized customer satisfaction rather than health. Secondly, to establish minimum flow rates as standards (e.g., as mentioned in Jaroszczyk I, noted above) would appear at least to require more precise definition. If the flow rate is increased by increasing the air velocity rather than the filter cross section, the residence time of any particular segment of a gas will decrease and by that assumption the filter xe2x80x9cefficiencyxe2x80x9d will decrease accordingly, as noted in Jaroszczyk II. Cited studies of filter efficiency also seem to be directed more towards demonstrating the greater efficiency of some particular company""s product rather than contributing to any understanding of the problem, since one cannot draw any general conclusions from comparisons of studies that in one case use air velocities of 5 cm/sec (Jaroszczyk II, cited above) while another uses air velocities of 0.75 m/sec (Lee, cited above).
Even reported efficiency values are difficult to interpret. That is, the American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc. (xe2x80x9cASHRAExe2x80x9d) defines one efficiency test method, while a newer penetration test by the xe2x80x9cDOPxe2x80x9d (dioctyl phthalate) method, DOP penetration being essentially the converse of the ASHRAE efficiency, may also be cited, and comparable values of these results are given in Table III below as set out by Hollingsworth and Vose Company (undated sales brochure) for a selection of that company""s products:
Using comparable methods, and taking this terminology at face value, an efficiency of 90-95% should mean a penetration rate of 5-10%, hence the figures just cited do not provide an adequate guide to filter performance except in purely relative terms.
In light of the foregoing, this inventor accordingly sought to develop and create an air purification device for use in vehicle cabins and elsewhere that would reduce the concentration levels of EPAxe2x80x94criteria pollutants therein to an amount at least less than the National Ambient Air Quality Standard (NAAQS) for each pollutant, as set by the EPA in terms of concentration levels above which the pollutant is presumed to create a health risk to human beings. The EPA had initially established a NAAQS for hydrocarbons, but that standard was subsequently abandoned in favor of a new category of air pollutants under the title xe2x80x9cToxics.xe2x80x9d Many hydrocarbons, including benzene, are toxic; benzene is indeed a Class A carcinogen, i.e. a proven human cancer causing agent. A study published by the South Coast Air Quality District in California determined that among all the air toxics measured inside the cabins of operating motor vehicles, benzene presented the greatest health risk for commuters in the Los Angeles basin. Therefore, it is an especially targeted pollutant for this invention.
Table IV below shows the pertinent NAAQS, the more stringent standards set by the State of California, or in the case of benzene, a standard set by The Netherlands for application in Europe (neither the EPA nor California appear presently to have an ambient air standard for benzene. Indeed at this time, as best known to the inventor, the EPA has set no ambient air standards for any toxics.)
(In Table IV, xe2x80x9cxcexcg/m3xe2x80x9d means xe2x80x9cmicrograms per cubic meter, xe2x80x9cppmxe2x80x9d means xe2x80x9cparts per million, xe2x80x9cppbxe2x80x9d means xe2x80x9cparts per billion,xe2x80x9d xe2x80x9cPM 10xe2x80x9d means a particle size of 10 micrometers or less in diameter, xe2x80x9cPM 2.5xe2x80x9d means a particle size of 2.5 micrometers or less in diameter, and the time periods on the right in the right hand column mean that measured concentration values averaged over the stated time periods should not exceed the standard shown in the middle column. These standards are set out in greater detail in FIG. 27.)
With respect to vehicle ventilation systems in general, in the experimental data to be discussed below, which indicate a reduction of air pollution to below defined standards when an embodiment of the present invention was in operation but pollution values in excess of the standards when that device was not in operation, measurements were made in a vehicle that had a filter system built in to its ventilation system and in most cases was in operation, but was not effective since the measured pollution levels when the embodiment of the invention then being used was not turned on still exceeded those standards.
Thus to this inventor, the prior art disclosed no systematic treatment of air purification technology that was at all adapted for application in vehicle cabins, but only the partial solutions as previously described. Suggestions as to what might ideally be done were not provided in any structural detail, evidently in light of the much greater emphasis on minimal xe2x80x9ccustomer satisfactionxe2x80x9d as a tool in marketing, and thus an unwillingness to invest in the development of truly effective filter systems. The data presented herein and elsewhere establish a long felt need, but one that is presently unmet. Thus, after experimenting with a variety of filter media, blowers and filter device designs and packaging, it occurred to the inventor that the sequence of filters could be as significant a factor as the type. Also, the structure of the filters ultimately employed by the inventor was made to combine two filtering processes, i.e., the xe2x80x9cpackagingxe2x80x9d for one filter medium was provided by another material that would itself contribute a significant filtering effect. A 7 m3/min (250 CFM) prototype of the invention having the desired filter sequence was then built and tested. Selected filter media packets were fabricated as hereinafter described and installed in the device, and their effectiveness was tested in the field in the Portland, Oreg. area. That same device was also tested in the Los Angeles area in August of 1999, when pollution was high. That prototype appears herein as the embodiment installed in the vehicle trunk as shown in FIG. 8.
Two smaller versions of that prototype were then constructed, one still with a 7 m3/min (250 CFM) rated blower, and the other with a 5 m3/min (176 CFM) blower. These two prototypes, that are described as the portable embodiment herein, were field tested in Los Angeles, Portland, and Bangkok, Thailand. Exemplary results of these tests are described and shown below with reference to corresponding figures. Additional tests not shown here were also carried out, the results of which were uniformly consistent with those reported here.
The invention provides air purification apparatus that reduces substantially the amount of specific major air pollutants found inside motor vehicle passenger cabins or similar environments, thus to provide a lessening of human health risk and increased comfort for passengers in motor vehicles or persons in those other environments. In a motor vehicle, the apparatus is not added to the existing ventilation system, but has its own blower, which preferably operates at variable speed on 12 volts direct current. A preferred embodiment of the apparatus is portable and can be installed in any vehicle, operating through power from a cigarette lighter outlet or similar power source, or it can be wired directly into the vehicle""s electrical system. In particular, in a multi-vehicle family, the air purifier is easily moved from one vehicle to another. The air purifier is of light weight, a preferred embodiment of which is adapted to be placed in the center of the rear seat where it can be secured by a seat belt, and can be used as a console and arm rest, with pouches thereon to hold personal articles, including the usual holders for small change, audio tapes and CDs, and also cup holders. If not desired for use as an arm rest or console, the device can be secured in any vacant seat location. Alternatively, the apparatus can be strapped to the floor, especially of a van or SUV (sport utility vehicle), or mounted in the trunk of a car using special ducting to draw air from the passenger cabin into the apparatus and thence from the apparatus back into the vehicle cabin.
A principal object of the invention is to maintain vehicle cabin air that is free of harmful levels of the respirable particles (fine particulate 2.5 microns and smaller in diameter size), noxious and/or toxic gases, and airborne infectious agents, which present substantial human health risk. The apparatus is not so limited in size or power that it has the severe pressure drop restrictions common to filters placed in the ventilation systems of vehicles. It substantially reduces specific incoming exhaust-related pollutants, as well as passenger-generated pollutants such as tobacco smoke, viruses and bacteria. The apparatus also has the substantial benefit of being able to filter and continuously re-filter air in the cabin, rather than have the filter operate on a one-pass basis as occurs within many ventilation system designs. The apparatus operates independently from, and will not adversely affect, any existing vehicle ventilation system.
Another object of the invention is to provide an air purifier device that operates as a high capacity linear air-flow system. The apparatus draws in cabin air through a large grate at a first end of an airtight housing, and then passes that air through an air conduit that contains 3 to 5 individually fabricated and aligned filter media packets that contain in a pre-determined sequence at least gross particulate media (i.e., some fine particulate material may also be captured), desiccants, adsorbents, chemisorbents, and catalysts, as well as a deep pleated HEPA particulate filter and a post-filter. (Except where the context indicates otherwise, the term xe2x80x9csorbentxe2x80x9d is used hereafter so as to encompass both adsorption and absorption). A 5 m3/min (176 CFM)xe2x80x947 m3/min (250 CFM) rated 12 volt DC blower pulls the air through that air conduit. The resulting air is then expelled through an outlet at the top of the purifier housing, which outlet may preferably be of about 7.6 cm. (3 inch) diameter. Wiring includes a switch to vary the blower speed, installed in series on an electrical cord that connects the air purifier with the cigarette lighter outlet in the vehicle or a similar power source. If portability of the device is not sought to be retained, the wiring can be connected directly to the vehicle electrical system. The blower is preferably shock mounted, using gaskets on either side of the motor mounting plate to reduce noise and provide air seals.
Yet another object of the invention is the reduction of cabin air pollutants to meet EPA, State of California, and European Ambient Air Quality Standards. That object is found to be accomplished through the use of a uniquely designed sequence of filter media packets that was especially conceived for this device. The preferred sequencing of filter media packets as shown below has been identified through repetitive testing, although the sequence can be modified to treat a less demanding pollutant mix targeted in certain geographical areas during particular seasons of the year:
1. Desiccant-sorbent packet containing various types of silica gel, zeolite and/or molecular sieves, within an at least gross particulate medium envelope.
2. Sorbent packet containing various types of packed activated carbon granules or pellets, within an at least gross particulate medium envelope. (The term xe2x80x9ccarbon particlexe2x80x9d is used hereinafter to encompass both pelletized and granular carbon, and also any other particulate forms of carbon as may be known to a person of ordinary skill in the art.)
3. Catalyst packet to break down carbon monoxide, within an at least gross particulate medium envelope. To function properly the catalyst packet must be preceded in the air-flow stream by desiccants to reduce moisture and by sorbents to capture sulfur and other acids which could poison the catalyst and make it inoperative.
4. Sorbent packet containing various types of coconut based activated carbon granules, beads, and/or powder, within an at least gross particulate medium envelope.
5. HEPA pleated filter (tested to remove 99.97% of particles measuring 0.3 microns in diameter, and more efficient for both smaller and larger particles), about 7.6 cm. (3 inches) deep.
6. A second filter of the type indicated in 4 above, or a coconut-based carbon impregnated fiber medium, to capture any residual gases and odors.
The use of the above filtering means in the indicated sequence will decrease passenger cabin air pollutants across a broad spectrum, and meet the specific health standards for ambient air shown above in Table I. In particular, the effective reduction of diesel exhaust fumes, which generally comprise fine particulate matter to which a variety of toxic and/or noxious substances are adhered, require both the sorbent filter media and the HEPA filter. The use of adsorbents and chemisorbents will filter out nitrogen oxides including nitrogen dioxide, sulfur oxides including sulfur dioxide, and many harmful hydrocarbons, especially including aromatic hydrocarbons such as benzene and toluene. The HEPA filter, which is essential for capturing and holding PM2.5 and smaller (the fine respirable) particles, will remove a wide range of pollutants, including the following:
a) heavy metals such as lead, cadmium, mercury and asbestos;
b) noxious gases that attach to tiny particles such as sulfate and nitrate precipitants from gasoline and diesel engines and coal fired utility plants;
c) disease-causing microorganisms, including both bacteria and viruses, as well as fungi.
The foregoing objectives are met by the present invention by providing the following features:
1. a uniquely effective and long-lasting filter sequence for removal of fine particles and specific gases inside vehicle cabins to meet government health standards for ambient air;
2. accomplishment of the above goal with a portable, stand-alone air purifier that can be installed in existing vehicles as an after-market add-on rather than being built into the ventilation system of new cars;
3. location of the purifier in a convenient and safe place inside the cabin, particularly in the center of the rear seat, so it also can serve as an armrest or console. This placement allows enough space for the device to be fitted with a powerful motor and many different filter media, hence the air circulation is sufficient to accomplish the filtration goal; and
4. alternative location of the purifier in the vehicle trunk, with ducted air fluidly connected to the vehicle cabin, a structure that isolates the blower from the vehicle passengers while still providing effective air purification and a convenient console.
Proper and most efficacious use of the apparatus (hereinafter designated as an air purifier) as well as adequate evaluation of its utility, requires an understanding of what are the relevant data, along with actual measurements of air purity. Reference in the prior art as to the number of times within so many minutes that the air within some particular volume is exchanged, even though that parameter is widely used as a marketing tool, provides no information whatever about the reduction of air pollution within a vehicle, given that such parameter could as well be used to describe the performance of a simple fan. The same is true of air flow rate standards, since the air flow rate is simply another way of expressing the rate of air exchange within a given volume. It is not some purported xe2x80x9cefficiencyxe2x80x9d of a filter that is sought, but rather a maximum removal of pollutant. That is accomplished in part by using the most effective filter media available, of course, but also by providing as much filter medium as may be practical, which relates to the number, cross-sectional area, and depth of the filters used.
The motor vehicle cabin also presents a particularly difficult problem in reducing air pollution, since the vehicle cabin is not a closed system, but xe2x80x9cnewxe2x80x9d air is continually being drawn into it through the vehicle ventilation system. Ventilation systems that have a xe2x80x9crecirculatexe2x80x9d mode will tend to decrease the amount of such xe2x80x9cnewxe2x80x9d air that is being drawn in, of course, but there will still be some amount of xe2x80x9cnewxe2x80x9d (and polluted) air being drawn in. It is thus only by a comparison of the air quality within the vehicle cabin at times that an air purifier is turned on, as compared to like data when no air purifier is operating, that any adequate measure of the performance of an air purifier can be acquired. (This also suggests, of course, that to attain higher purity air within a vehicle cabin, the ventilation systems should in fact be operated in that xe2x80x9crecirculatexe2x80x9d mode.)